1. Field of the Invention
The present invention relates to two-piece solid golf ball in which a polyurethane material serves as a cover-forming material; and more particularly to a golf ball which provides a highly satisfactory shot feeling on being hit and excellent controllability, which has improved flight performance, and which exhibits excellent cut resistance (i.e., durability when topped with an iron), scratch resistance, and durability against cracking caused by repeated hitting.
2. Description of the Related Art
Conventionally, various two-piece solid golf balls have been proposed in order to meet demands from professional golfers and advanced golfers. For example, Japanese Patent Application Laid-Open (kokai) No. 6-319830 (Japanese Patent No. 2576787) discloses a golf ball designed such that the value obtained by dividing the core hardness by the ball hardness, and the thickness of the cover fall within specific ranges, to thereby improve carrying distance, feeling on impact, and spin property. However, in the golf ball disclosed in this publication, since the cover is formed from an ionomer resin, the cover exhibits poor scratch resistance. In addition, the restitution of the core is insufficient, and there is still room for improvement in terms of carrying distance.
Japanese Patent Application Laid-Open (kokai) No. 9-308708 discloses a two-piece solid golf ball designed such that the thickness, flexural rigidity, and Shore D hardness of the cover fall within specific ranges, to thereby improve feeling on impact and controllability without lowering restitution and cut resistance. However, since the cover of this golf ball predominantly contains an ionomer resin, there is still room for improvement in terms of scratch resistance of the cover. In addition, the carrying distance, feeling on impact, and controllability of this golf ball are not simultaneously improved sufficiently, since properties of the core are not specified.
Meanwhile, Japanese Patent Application Laid-Open (kokai) No. 9-215778 discloses a two-piece solid golf ball having a cover formed from a polyurethane material. However, in this golf ball, since the cover is thick, the restitution of the core is insufficient, and the scratch resistance of the resin used for forming the cover is unsatisfactory, there is still room for improvement in terms of carrying distance and scratch resistance of the cover.